SITE-DEPENDENT DISTRIBUTION OF MACROPHAGES IN NORMAL HUMAN EXTRAOCULAR-MUSCLES

Purpose. Clinical data indicate that extraocular muscles have differen t susceptibilities for some orbital immune disorders depending on thei r anatomic location. The resident immunocompetent cells may be importa nt mediators in the local pathogenesis of such disorders so the distri bution of these cells was studied in extraocular muscles obtained from normal human donors. For comparison skeletal muscles were studied. Me thods. The cell distributions were analyzed quantitatively in cryostat cross-sections subjected to a two-step immunoperoxidase method using monoclonal antibodies against T cells, B cells, macrophages and severa l other markers for cell differentiation or activation. The macrophage distribution was analyzed in more detail using on-line semiautomatic image analysis equipment (VIDAS, Kontron, Elektronik GmbH, Eching, Ger many). Results. Extraocular muscles contain numerous macrophages, fewe r human leukocyte antigenD-related (HLA-DR) positive cells and T cells , whereas B cells are absent. Th numeric density of all cell types, an d macrophages in particular, is much higher in extraocular muscles tha n in skeletal muscles. In extraocular muscles the majority of T cells are positive for the CD8 antigen (suppressor/cytotoxic), in skeletal m uscle CD4 positive T cells (helper) predominate. Conclusions. Extraocu lar muscles contain many more CD8-positive cells and macrophages per s quare millimeter than skeletal muscles. Of all the cell types studied, only the macrophage distribution differs significantly among the norm al extraocular muscles: the medial and inferior recti muscles contain about twice as many macrophages as the lateral rectus and superior obl ique muscles. Their mean sizes (area) or shape distributions however, appear to be similar.